Apparatus and method for noncontact measurement of the velocity of a moving mass

ABSTRACT

The specification discloses an apparatus and method for measuring the velocity of a moving mass. A noncontact heat source, such as a high powered infrared laser, intermittently heats and creates a hot spot on the moving mass in a first position in space. The heat source remains out of contact with a moving mass while heating it. A noncontact detector, such as an infrared heat detector, detects the hot spot at a second position in space and remains spaced apart from second position while detecting the hot spot. The second position is spaced a predetermined distance from the first position and, with respect to the first position, is disposed in the direction of the travel of the moving mass. The noncontact detector generates a detection signal when the hot spot is in the second position, and a monitor is responsive to the detection signal to determine when the hot spot is in the second position. The monitor also determines when the hot spot is created at the first position and it generates a monitor signal corresponding to the time elapsed (transit time) while the moving mass traveled from the first position to the second position. Thus, the monitor signal corresponds to the velocity of the moving mass.

FIELD OF INVENTION

The present invention relates to an apparatus and method for measuringvelocity and particularly relates to an apparatus and method formeasuring the velocity of a moving mass without contacting the mass.

BACKGROUND AND SUMMARY OF INVENTION

Velocity measurement of a moving masses is necessary for many industrialoperations and in many applications noncontact velocity measurement ispreferred or required. For example, a noncontact measurement is requiredwhere a contacting measurement device would interfere with the normalfunction or operation of the moving mass, where space on or around themass is limited, or where the moving mass cannot accept any foreignobjects. The present invention is an improved noncontact apparatus ofmethod for measuring such velocity, and as used herein, the term"noncontact" is used to mean that there is no mechanical contact withthe moving mass and no object or other material is attached to orintroduced into the moving mass.

Many contact and noncontact methods of measuring the velocity of amoving mass are known. One of the most common types of velocitymeasurement involves the measurement of some property of a moving massat two points along the direction of movement. For example, thereflective properties, the temperature or the density of the moving massmay be examined at two points to determine velocity. These methodsusually depend on the existence of fluctuations in those properties (offaverage conditions) around their average values and the propagations ofsmall volumes of these off average conditions for some distance alongthe direction of movement or flow. These off average conditions may beanalyzed at two points to determine transit time. For example, in onesuch device two light sources and two light sensors are used to monitora moving mass at two different points along the travel path of themoving mass. One source and sensor monitor reflective light from themass at one point along the travel path and the other source and sensormonitor reflective light at another point which is down stream from thefirst point. Because of surface inhomogeneities, the reflected lightwill be different when reflected from different positions on the movingmass. However, since the two source and sensor pairs are monitoring thesame moving mass, and assuming that surface conditions do notsignficantly change between the first and second positions, the signalsproduced by each pair should be the same or similar, but time shiftedone with respect to the other. The time shaft between these two signalsis analyzed to determine the transit time between the two points and,thus, determine velocity.

In another method, a detectable object, such as a reflector, is placedon a moving object, usually a rotating object, and it is illuminated.The light reflected from the moving reflector is then analyzed todetermine velocity.

In yet another velocity measurement technique that is commonly used todetect fluid flow velocity, a heater is placed into the flowing fluidand the heater is modulated so that the heat produced is changing over aperiod of time. A heat sensor is disposed in the fluid downstream fromthe heater to detect the heat fluctuations in the fluid and to produce asignal. The signal produced by the heat sensor will be time shifted withrespect to the modulation of the heater, and this time shift may beanalyzed to determine the transit time of the fluid between the heaterand the sensor.

While known techniques for measuring velocity of moving masses have beenadequate for many applications, the present invention generally offerssignificant advantages over such techniques and is more flexible interms of the applications for which it is suited. For example, placing atemperature probe and a heater in a moving stream of fluid may causeturbulence or other undesirable disturbances in the fluid flow. Thesedisturbances may create inaccuracies in flow measurement or have otherundesirable consequences unrelated to velocity measurement. The presentinvention avoids creating such disturbances by not contacting the movingmass. Also, in most cases, it would not be practical to insert heatersand heat sensors in a flow of solid objects or a slurry flow. Thesensors would impede the movement or flow of the objects, and the solidobjects may destroy the heaters and sensors. Likewise, these problemsare overcome in the present invention because it does not require anytype of contact with the moving mass.

The reflected light technique described above depends on the reflectivecharacteristic of the moving mass which usually means that it depends onthe surface characteristics thereof. In some situations the surfacecharacteristics are changing very rapidly, and if these changes aresufficient, it may be impossible to correlate signals generated byreflections from the moving mass at two points along the travel path.Since the present invention does not rely on surface characteristics,this problem is avoided.

In accordance with the present invention, an apparatus for measuring thevelocity of a moving mass having a direction of travel includes anoncontact heat source. The heat source intermittently heats and createsa hot spot on the moving mass at a first position in space, and duringthe heating operation, the heat source remains out of contact with themoving mass. A noncontact detector is also provided for detecting heatat a second position in space, and during the detection operation, thedetector remains spaced apart from the second position. The secondposition is spaced a predetermined distance apart from the firstposition and, with respect to the first position, the second position isdisposed in the direction of travel of the moving mass. As the masspassed by, the detector is operable to detect and generate a detectionsignal when the hot spot is in the second position. A monitor system isprovided for monitoring when a hot spot is created on the moving mass inthe first position and for monitoring the detection signal to determinewhen the hot spot is in the second position. The monitor system thengenerates a monitor signal that corresponds to the time elapsed whilethe hot spot on the moving mass travels from the first position to thesecond position, and, thus, corresponds to the velocity of the movingmass.

In the preferred form, the noncontact heat source is an infrared lightsource and the noncontact heat detector is an infrared heat detector.Also, in order to improve reliability, a band pass filter is used tocondition the detection signal. Background light and heat sources willbe detected by the detector and in response to this background noise, alow frequency signal will be generated. In contrast, the hot spot on themoving mass when detected by the detector, will cause a sudden jump inthe detection signal and will have a high frequency. The band passfilter is chose to pass the relatively high frequency signals createdwhen the hot spot enters the second position and to reject therelatively low frequency signal created by background noise.

In accordance with another aspect of the preferred form of the presentinvention, the velocity of the moving object is determined by looking atseveral transit times of several hot spots moving from the first to thesecond positions. This plurality of transit times is processed using across correlation function to calculate the velocity of the moving mass.

In accordance with yet another aspect of the preferred form of thepresent invention, a second infrared light detector may be used todetermine when the heat source is creating a hot spot. This infraredlight detector would simply monitor the output of the infrared heatsource and would provide a signal as part of the monitor system toindicate when the hot spot is being created. Alternatively, the monitorsystem could simply monitor the power to the radiant heat source and usethe power signal to determine when the heat source is creating the hotspot.

In the preferred form of the present invention, the detector includes amicrometer mounting system for adjusting the position of the detector sothat the distance between the heat source and the detector may beprecisely maintained. An electronic caliper is provided to constantlymonitor the position of the heat detector and provides such positioninformation back to the monitor system. Finally, as an aid to thepositioning of the heat detector, an aiming light is mounted on the heatdetector to transmit a beam of light to indicate the path and positionthat will be detected by the heat detector.

In addition to the apparatus described above, the invention encompassesthe methods that are performed by the above described apparatus formeasuring the velocity of a moving mass.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may best be understood by reference to thefollowing detailed description of preferred embodiments of the presentinvention when considered in conjunction with the Drawings in which:

FIG. 1 is a schematic diagram of a noncontact velocity measurementapparatus showing a moving object, a heat source and a heat detector;

FIG. 2 is schematic diagram of a noncontact velocity measurementapparatus configured to measure the rotational velocity of a rotatingobject;

FIG. 3 is a block diagram of the noncontact velocity measurementapparatus illustrating its electronic operation;

FIGS. 4a and 4b graphically illustrate typical signals from a lightmonitor which monitors an infrared heat source and from an infrareddetector;

FIGS. 5a and 5b illustrate typical filtered signals from the lightmonitor and infrared heat detector;

FIGS. 6a and 6b illustrate trigger signal generation based on the lightmonitor signal and the infrared detector signal;

FIGS. 7a and 7b illustrate typical filtered signals from the lightmonitor and the infrared detector for multiple episodes; and

FIG. 8 illustrates a typical cross correlation function between thelight signal and the infrared detector signal based on multipleepisodes.

DETAILED DESCRIPTION

Referring now to the drawings in which like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIG. 1 a noncontact velocity measurement apparatus 10that includes an heat source 12 and heat detector 14. In its preferredform, the infrared heat source 12 is a high intensity carbon dioxidelaser that focuses its beam toward a moving mass 16 that is moving alonga travel path indicated by the arrow 18. Although the mass 16 isdepicted in FIG. 1 as a solid object, it will be understood that theinvention may be used with many different types of moving masses,including fluid, suspensions, slurries, and the like, but the presentinvention is best suited for use with moving solid objects. The heatsource 12 focuses its beam on the moving mass 16 to create a hot spot 20thereon, and the hot spot will move with the moving mass 16 in thedirection indicated by the arrow 18. In FIG. 1, a second hot spot 22 isshown in position beneath the detector 14. This hot spot 22 waspreviously created by heat source 12 and has moved to the positionindicated by hot spot 22 for detection. The distance between the heatsource 12 and the detector 14 is chosen so that the hot spot 22 will besubstantially similar to the hot spot 20. That is, taking intoconsideration the conductive properties of the moving mass 16, theexpected heat transferred due to convection and radiation, and the speedof the moving mass 16, the hot spot 22 will remain relatively unchangedas it moves from adjacent the heat source 12 to a position adjacent tothe detector 14. One concept basic to the present invention is that thetime of the creation of the hot spot 20 by the source 12 will bemonitored, as will the time of detection of the same hot spot by thedetector 14, and the transit time of the hot spot 20 traveling from thesource 12 to the detector 14 will be calculated. This transit time willindicate the velocity of the moving mass 16.

The monitoring function is provided by the processor 24 which alsofunctions as a power supply. The processor 24 is connected by line 26 toa light detector 28 that is focused on the output of the heat source 12.The function of the light detector 28 is to create a signal indicatingthat the heat source 12 is on and is creating a hot spot, and thisinformation is fed back to the processor 24. Line 30 represents theinterconnection between processor 24 and heat source 12 through whichdata is transferred and power is supplied to the heat source 12. (Theterm "line" as used herein and shown in the drawings may represent morethan one interconnection even though shown or referred to as single). Inan alternate embodiment, line 30 could be monitored to determine power"on" and power "off" conditions and, thus, to indirectly determine whenthe heat source 12 is creating a hot spot 20 of the mass 16. In eithercase, the processor 24 is continuously updated as to the time ofcreation of each hot spot 20 by the source 12.

A line 32 reprsents the connection from the processor 24 to the detector14 for supplying power to the detector 14 and for feeding a detectionsignal from the detector 14 back to the processor 24. This detectionsignal corresponds to the heat detected by the infrared heat detector 14and, thus, would include signals indicating the presence or absence of ahot spot 22 in a detection position adjacent to the detector 14. In thismanner, the processor 24 is continuously provided with information as towhen the hot spots 22 are detected.

Line 34 connects the processor 24 to a linear position monitor referredto herein as a caliper 36 that is mechanically interconnected with thedetector 14 to continuously provide position data to the processor 24.In the preferred embodiment, both the heat source 12 and the detector 14are mounted on a mounting rod 38 that will control the distance betweenthem. A micrometer 40 is connected to the mounting rod 38 and to thedetector 14 so that by adjusting the micrometer 40, the relativepositions of, and the distance between, the source 12 and the detector14 may be precisely controlled. As the micrometer 40 is adjusted to movethe detector 14, the amount of movement of the detector 14 and the newposition of the detector 14 is provided to the processor 24 by data fromthe electronic caliper 36. Thus, the processor 24 is continuouslyprovided with the precise distance between the source 12 and thedetector 14.

In order to facilitate the positioning of the detector 14, it includesan aiming light 42 mounted thereon to direct a beam 44 along thedetection direction. The detector 14 is designed so that it will detectinfrared radiation emanating from a specific position. Thus, it willdetect infrared radiation traveling up the path indicated by the beam44. In order to properly position the detector 14, it is moved so thatthe beam 44 will illuminate the expected position of hot spots 22 thatare initially created by the source 12.

Referring now to FIG. 2, there is shown an alternate embodiment of theinvention in which the noncontact velocity measurement system 10 ismodified and mounted to detect the angular velocity of a rotating object46 that is rotating about an axis of rotation 48 in the directionindicated by the arrow 50. In this embodiment, the source 12 and thedetector 14 are mounted equidistantly from the axis of rotation 48 byarms 52 and 54, respectively. Thus, the detector 14 and the source 12are positioned on the same circular path of rotation as indicated by thedotted circle 56. A hog spot created by the source 12 will travel alongthe circular travel path 56 past and adjacent to the detector 14.

In this embodiment, the caliper 36 is pivotally connected at two ends tothe arms 52 and 54 so that it will measure a linear distance between thearms 52 and 54 and it is calibrated so that the output of the caliper 36corresponds to the angular distance, as indicated by arrow 58, betweenthe two arms 52 and 54. Thus, the output of the caliper 36 will provideto the processor 24 the angular distance between the source 12 anddetector 14. The transit time of a hot spot as it travels from thesource 12 to the detector 14 is determined as described above withrespect to the embodiment shown in FIG. 1, and using this transit timeinformation and the angular distance 58, the processor 24 calculates theangular velocity of the rotating object 46.

Referring now to FIG. 3, there is shown a block diagram of the velocitymeasurement system 10 which graphically illustrates the electronicoperation of this system. The heat source 12 is connected by line 30 toa power supply and timer 60 that includes an internal clock thatintermittently powers the heat source 12 on and off. A control line 62is connected between the power and timer 60 and a transit time analyzer64. Control signals are transmitted to the power and timer 60 over aline 62 and trigger signals are supplied by the power and timer 60 overthe line 62 back to the transit time analyzer 64 so that the analyzer 64can indirectly determine when the heat source 12 is turned on.

The light sensor 28, which senses the output of the heat source, isconnected by line 26 to a signal conditioner 65 and the output signalconditioner 65 is provided on line 66 to the transit time analyzer 64.In the preferred mode, the signal conditioner 65 is a band pass filterthat passes high frequencies and rejects low frequencies. Backgroundnoise and ambient light will represent relatively low frequencies and,when the heat source 12 turns on, the abrupt change in light detected bythe sensors 28 will represent a high frequency that will be passed bythe signal conditioner 65 to the transit time analyzer 64 indicatingthat the heat source 12 turned on. Likewise, when the heat source 12turns off, the abrupt change will represent a high frequency signal thatwill be passed to the analyzer 64 indicating that the source 12 is"off."

In like manner, the detection signal from the detector 14 is transmittedby line 32 to a signal conditioner 68 whose output is supplied on line70 to the transit time analyzer 64. The signal conditioner 68 is alsopreferably a band pass filter that passes high frequency signals andrejects low frequency signals. When the hot spot moves into detectionposition, such as hot spot 22 shown in FIG. 1, it will create an abruptchange in the output of the detector 14 representing a high frequencysignal and when the hot spot moves out of detection position, anotherabrupt change in the output of the detector 14 will represent anotherhigh frequency signal. These two high frequency signals are passed bythe signal conditioner 68 to the transit time analyzer 64 indicatingwhen the hot spot appeared at the detection position and when it leftthe detection position. Again, the relatively low frequencies producedby ambient light and heat and background noise will be rejected by thesignal conditioner 68. The transit time analyzer is also supplied withdistance information as to the distance between the source 12 and thedetector 14 by the caliper 36 through line 34. Thus, the transit timeanalyzer is supplied with the time at which the source 12 is turned on,the time at which the hot spot appears at the detector 14, and thedistance between the source 12 and the detector 14. Using thisinformation, the transit time analyzer calculates the velocity of themoving mass 16 and supplies that information on line 72 to the computer74. The computer 74 can store the information, or output it in a numberof forms. In the preferred form, the computer 74 will transmit the rawdata obtained by the transit time analyzer 64 through an analog output76. It will also convert the data to a digital form and transmit it to adigital output 78 and, after calculating the velocity of the movingmass, it will transmit that data to a digital display 80 and cause it tobe visually displayed.

Referring now to FIGS. 4a and 4b, there are shown typical signals fromthe light monitor 28 (FIG. 4a) and the infrared detector 14 (FIG. 4b).In these Figures, the horizontal axis indicates time and the verticalaxis indicates the amplitude of the signals. In FIG. 4a, the leadingedge 82 of the square wave 83 indicates the time at which the source 12was powered on; the trailing edge 84 indicates the time at which thesource 12 was powered "off" and the width 86 of the square wave 83indicates the time during which the source 12 remained on. Likewise, inFIG. 4b, the leading edge 88 of the square wave indicates when thedetector 14 first detected the hot spot 22; the trailing edge 90indicates when the hot spot 22 moved out of detection position adjacentthe detector 14, and the distance 92 represents the time during whichthe hot spot was being detected by the detector 14. Referring to bothFIGS. 4a and 4b, it will be appreciated that the signal from theinfrared detector 14 (square wave 83) is time shifted with respect tothe signal from the light monitor 28 (square wave 89). This time shiftindicates the time that was required for the hot spot to travel from theheat source 12 to the detector 14.

FIG. 5 graphically illustrates the typical filtered signals from thelight monitor 28 and the infrared detector 14. FIG. 5a shows the lightmonitor 28 signals as they would appear after passing through the signalconditioner 65 and FIG. 5b shows the detector 14 signal after it haspassed through the signal conditioner 68. Referring to FIG. 5a, thespike 94 represents the high frequency signal corresponding to theleading edge 82 and the spike 96 represents the high frequency signalcorresponding to the trailing edge 84 as shown in FIG. 4a.

Likewise, with regard to the signal from the infrared detector 14, FIG.5b shows a spike in 98 that corresponds to the high frequency signal iscreated by the leading edge 88 and (FIG. 4b) the spike 100 representsthe high frequency signal created by the trailing edge 90 (FIG. 4b). Thespikes 94-100 may be used to calculate the transit time of the hot spotas it moves from the radiant heat source 12 to the detector 14.

As shown in FIGS. 6a and 6b, it is preferred to use the spikes 94 and 98to determine transit time. In order to determine when the heat source 12turns on, a trigger level 102 is chosen so that whenever the spike 94appears, a starting time t1 as indicated by the dashed line 104 wil bedetermined.

In like manner, at arbitrary trigger level 106 is chosen for analyzingthe conditioned signal from the detector 14. Whenever the spike 98appears, it will exceed the trigger level 106 and a time t2 as indicatedby a dashed line 108 will be established indicating the moment at whichthe hot spot was first detected by the detector 14. The differencebetewen t1 and t2 will be the transit time of the hot spot as it travelsfrom the heat source 12 to the detector 14.

It will be appreciated that the spikes 96 and 100 could also be used todetermine the transit time, or the transit time could be determinedusing a combination of the spikes 94, 96, 98, and 100 using an averagingor correlation technique. In most applications, it will be preferable tomonitor a plurality of episodes in order to determine the velocity ofthe moving mass 16.

FIGS. 7a and 7b show, respectively, the conditioned signals that wouldbe produced by the light monitor 28 and the detector 14 for threeepisodes or cycles.

Perhaps the most accurate way to determine transit time would be todetermine a cross correlation between the light monitor 28 signal andthe detector 14 signal as shown in FIGS. 7a and 7b, respectively. FIG. 8illustrates a typical cross correlation function between the lightmonitor 28 signal and the detector 14 signal. In this Figure, thevertical axis represents correlation between the two signals and thehorizontal axis represents time. The peak of the pulse 110 occurs at thetime t1 which corresponds to the transit time of the hot spot as itmoves from the heat source 12 to the detector 14.

As previously mentioned, the velocity of the moving mass 16 could bedetermined with a single heat/detect episode as shown in FIG. 5, butmultiple episodes will normaly be used and averaging could be used toimprove accuracy. However, even when averaging is performed, there willbe some uncertainty in the velocity measurement because the selection ofthe trigger levels 102 and 106 (FIG. 5) cannot be made perfectly. Toovercome this problem, it is preferred to use more advanced signalprocessing methods such as cross correlation. The cross correlation C₁₂(t) function is given by: ##EQU1## where

    ______________________________________                                        C.sub.12 (T)                                                                              = cross correction function                                       T           = lag time                                                        P           = analysis time                                                   x,y         = signals                                                         t           = time                                                            ______________________________________                                    

Using this cross correlation function, the transit time may bedetermined as graphically illustrated in FIG. 8.

Although described above with respect to particular embodiments, it willbe understood that the invention is capable of numerous rearrangements,modifications or substitutions of parts without departing from the scopeof the invention. The above detailed description is not intended as alimitation on the scope of the invention.

What is claimed is:
 1. An apparatus for measuring the velocity of amoving mass having a direction of travel, comprising:noncontact heatsource means for intermittently heating and creating a hot spot in themoving mass at a first position in space, said noncontact heat sourcemeans remaining out of contact with the moving mass when heating themass; noncontact detector means for detecting heat in the moving mass ata second position in space and remaining spaced apart from the secondposition in space when detecting, said second position being spaced apredetermined distance apart from said first position and, with respectto said first position, being disposed in the direction of travel of themoving mass; said noncontact detector means being operable to detect thepresence of the hot spot in the moving mass when the hot spot reachesthe second position and to generate a detection signal when the arrivalof the hot spot at the second position is detected; and monitor meansfor monitoring the time at which a hot spot is created on the movingmass in the first position, for monitoring the time at which thedetection signal indicates that the hot spot has reached the secondposition, and for generating a monitor signal corresponding to the timeelapsed during movement of the hot spot from the first position to thesecond position to enable a determination of the velocity of the movingmass.
 2. The apparatus of claim 1 wherein:said noncontact heat source isan infrared light source; and said noncontact detector is an infraredheat detector.
 3. The apparatus of claim 1 wherein:said noncontact heatsource is an infrared light source; said noncontact detector is aninfrared detector; and said moving mass is a solid object.
 4. Theapparatus of claim 1 further comprising a band pass filter for receivingand filtering the detection signal for passing relatively high frequencysignals created by the presence of the hot spot at the second positionand for rejecting relatively low frequency signals created by ambientlight conditions.
 5. An apparatus for detecting the velocity of a movingsolid object having a travel path and a travel direction, comprising:aradiant heat source disposed adjacent to, but spaced apart from, thetravel path for intermittently heating and creating a hot spot on thesolid object; means for detecting the time at which the radiant heatsource creates the hot spot on the object and for generating an onsignal corresponding to the time at which the hot spot is created; aradiant heat detector disposed adjacent to, but laterally spaced apartfrom, the travel path and being positioned down stream in the traveldirection from said radiant heat source, said radiant heat detectorbeing configured to detect the heat on the solid object in the path ofmovement of the hot spot and to generate a detection signalcorresponding to the magnitude of the heat detected on the solid object;means for mounting said radiant heat detector at a predetermineddistance from said said radiant heat source; detection circuitryconnected to receive the detection signal and being configured toanalyze the detection signal to determine the presence of the hot spotin the travel path adjacent to the detector based on a predeterminedchange in the detection signal and to generate a presence signalcorresponding to the time that the presence of the hot spot isdetermined; and velocity calculation means responsive to the on signaland the presence signal for determining the elapsed time between the onand presence signals and for calculating the velocity of the objectbased on the elapsed time and the predetermined distance between saidheat detector and heat source, and for generating a velocity signalcorresponding to said velocity.
 6. The apparatus of claim 5 furthercomprising output means responsive to the velocity signal for outputtingthe velocity of the moving object.
 7. The apparatus of claim 5 whereinsaid detection circuitry further comprises band filters for rejectingrelatively low frequency signals and thus discriminating againstbackground light and passing relatively high frequency signals generatedby the presence of the hot spot adjacent to said radiant heat detector.8. The apparatus of claim 5 wherein said means for mounting furthercomprises:means for adjusting said predetermined distance; and means forinputting said adjusted predetermined distance to said velocitycalculation means.
 9. The apparatus of claim 8 wherein said means foradjusting further comprises a micrometer attached to said radiant heatdetector.
 10. The apparatus of claim 5 further comprising an aiminglight mounted on said radiant heat detector to illuminate the locationin the travel path which is sensed by the heat detector.
 11. Theapparatus of claim 5 wherein said velocity means further comprises crosscorrelation calculation means for processing a plurality of on signalsand presence signals using a cross correlation function to calculate thevelocity of the object.
 12. The apparatus of claim 5 wherein said meansfor detecting comprises a second radiant heat detector configured todetect when the radiant heat source is heating.
 13. The apparatus ofclaim 5 wherein said means for detecting comprises means connected tosaid radiant heat source for determining when said radiant heat sourceis receiving power.
 14. An apparatus for detecting the angular velocityof a rotating solid object comprising:a radiant heat source disposedadjacent to, but spaced apart from, the rotating solid object forintermittently heating and creating a hot spot on the solid object, saidhot spot traveling in a circular travel path; means for detecting thetime at which said radiant heat source creates the hot spot on therotating solid object and for generating an on signal corresponding tothe time at which the hot spot is created; a radiant heat detectordisposed adjacent to, but laterally spaced apart from, the rotatingsolid object and being positioned adjacent to the circular travel pathand downstream from said radiant heat source, said detector beingconfigured to detect the heat on the solid object in the path ofmovement of the hot spot and to generate a detection signalcorresponding the magnitude of the heat detected on the solid object;means for mounting said radiant heat detector at a predetermined angulardistance along said circular travel path from said radiant heat source;detection circuitry connected to receive the detection signal and beingconfigured to analyze the detection signal to determine the presence ofthe hot spot in the circular travel path adjacent to the detector basedon a predetermined change in the detection signal and to generate apresence signal corresponding to the time that the presence of the hotspot is determined; and velocity calculation means responsive to the onsignal and to the presence signal for determining the elapsed timebetween the on and presence signals of the hot spot as it passes fromthe radiant heat source to the radiant heat detector and for generatingan angular velocity signal based on the elapsed time and thepredetermined distance between said heat detector and heat sourcecorresponding to the angular velocity of the rotating solid object. 15.A method for measuring the velocity of a moving mass having a directionof travel, comprising:intermittently heating and creating a hot spot inthe moving mass at a first position in space without contacting themoving mass when heating; detecting heat in the moving mass at a secondposition in space that is a predetermined distance apart from said firstposition and, with respect to said first position, said second positionin space being disposed in the direction of travel of the moving massand in the path of movement of the hot spot so that arrival of the hotspot of the second position is detected; generating a detection signalat the time the arrival of the hot spot at the second position isdetected; monitoring the time at which the hot spot is created in themoving mass at the first position; monitoring the time at which thedetection signal is generated; and generating a monitor signal whichcorresponds to the time elapsed between the time at which the hot spotis created and the time at which the hot spot arrives at the secondposition to facilitate a determination of the velocity of the movingmass.
 16. A method for detecting the velocity of a moving solid objecthaving a travel path and a travel direction, comprising;intermittentlyheating and creating a hot spot on the moving solid object with a beamof radiant heat; detecting creation of the hot spot on the solid objectand generating an on signal to indicate the time at which creation ofthe hot spot is detected; detecting heat on the solid object in thetravel path of the hot spot downstream in the travel direction at apredetermined distance from the point at which the hot spot was created;generating a detection signal corresponding to the magnitude of the heatdetected on the solid object; analyzing the detection signal todetermine the presence of the hot spot based on a predetermined changein the detection signal, and generating a presence signal to indicatethe time of said pesence; and determining time elapsed between the timeat which creation of said hot spot is detected and the time at which thepresence of said hot spot at said detection location is determined andcalculating the velocity of the moving object based on the elapsed timeand the predetermined distance.